1. Field of the Invention
The present invention relates to systems for routing data through one or more networks. More specifically, the invention provides a system for routing data packets through a network using router identification information contained in the data packets.
2. Background
Data communication networks may include various nodes, routers, switches, hubs, and other network devices coupled to and communicating with one another. Data is communicated between network devices by utilizing one or more communication links between the devices. A particular data packet (or data cell) may be handled by multiple network devices and cross multiple communication links as it travels between its source and its destination. Additionally, multiple networks may be coupled to one another by common network devices or common links.
Various protocols may be used to communicate routing information through a network. One type of protocol is referred to as a link state protocol, in which each node in the network knows the network topology such that the node can calculate routes through the network using the known topology. The link state information is distributed to network nodes using a series of Link State Advertisements (LSAs) originated by routers and other nodes in the network. For example, a router may advertise LSAs into the network area in which the router resides. These advertised LSAs may indicate that the router has connections to one or more network nodes. These LSAs are received by other routers and nodes in the network. Thus, the other routers and nodes learn of the connections described in the advertised LSAs. All routers in the network may generate and advertise similar LSAs.
Since each router "learns" the network topology by receiving various LSAs, each router is capable of independently calculating routes through the network. Typically, when a router forwards a packet, the router determines the best "next hop" router by consulting a routing table maintained by the router. Known routing systems use the data packet's destination address as the lookup key in the routing table to determine the next hop router. Since the exact destination address may not be stored in the routing table, the router selects the closest match. This type of matching may be time consuming, especially if the routing table has a significant number of entries.
Another routing approach, referred to as "tag switching" (or "tag routing"), forwards data packets based on "tags" inserted into the data packet rather than based on a packet's destination address. The router then uses a "tag table" to lookup the tag. Each tag in the tag table is bound to a route. Each tag-route pair must be distributed to other nodes in the network before the "tag switching" system can be used. This binding of tags and routes, and the advertisement of the tag-route pairs may take additional time, thereby delaying the transmission of network data. Additionally, each change in a tag-route pair must be advertised to other nodes in the network.
It is therefore desirable to provide a system capable of performing tag switching, but that does not require the binding of tags and routes, and does not require the advertisement of the tag-route pairs to other nodes in the network.